Changing pH shifts the microbial source as well as the magnitude of N2O emission from soil

Elizabeth M. Baggs, Claire L. Smales, Emma J. Bateman

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Abstract

Here, we examine the effect of long-term pH differences and short-term pH change on N2O emissions from soil, and the microbial source (ammonia oxidation versus denitrification) of N-15-N2O emissions. N-15-fertiliser (20 g N m(-2); 10 atom% excess N-15) was applied to (1) a silt loam soil of pH 7 held at 50% and 65% water-filled pore space (WFPS) (experiment 1) and (2) a loamy sand soil maintained at pH 4.5 and pH 7 for over 40 years (experiment 2). Soils were limed with CaCO3 or acidified with H2SO4, and comparisons were made with unadjusted soils. Ammonia oxidation was the main microbial source of N-15-N2O in soils limed to pH 7.0-8.1, unadjusted pH 7.1 (Experiment 1) and long-term pH 7 (experiment 2) soils. Eighty percent of N-15-N2O from the long-term pH 4.5 soil (experiment 2) was derived from denitrification suggesting a possible inhibition of N2O reduction. Short-term acidification to pH 5.6 or 4.3 lowered N2O emissions. Liming of the pH 4.5 soil resulted in over four times greater N2O emission (11 mg N14+15-N2O m(-2) over 41 days) than from the long-term pH 7.0 soil (experiment 2), with an associated increase in ammonia oxidiser-N2O and decrease in denitrifier-N2O production. This is the first report of a pH-induced change in microbial source of N2O. Our results highlight the importance of distinguishing between short- and long-term effects of pH management when predicting N2O emissions from soil, as they exhibit predominance of different microbial groups in N2O production, with likely adaptation of the microbial community.

Original languageEnglish
Pages (from-to)793-805
Number of pages13
JournalBiology and Fertility of Soils
Volume46
Issue number8
DOIs
Publication statusPublished - Oct 2010

Keywords

  • Ammonia oxidation
  • Denitrification
  • Liming
  • Nitrous oxide
  • pH
  • Stable isotopes
  • ammonia-oxidizing bacteria
  • nitrous-oxide production
  • 2 agricultural soils
  • grassland soil
  • DI-nitrogen
  • forest soil
  • varying PH
  • denitrification
  • nitrification
  • oxidation

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